1. Field of the Invention
The present invention relates to a tone generating apparatus for use in an electronic keyboard, electronic piano, synthesizer and so forth. More particularly, this invention pertains to a tone generating apparatus which generates musical tones by repeatedly reading out tone wave data stored in advance in a memory.
2. Description of the Related Art
There is a tone generating apparatus which sequentially reads out tone wave data from a wave memory and puts the data through tone generation or tone-ON processing to thereby generate musical tones.
Such a conventional tone generating apparatus is designed such that tone wave data corresponding to every waveform from the rise or attack portion of a musical tone to the end or release portion thereof is stored in advance in the wave memory and these pieces of tone wave data are sequentially read out from the beginning to prepare an associated tone signal, thus providing a continuous or sustaining musical tone.
The tone generating apparatus employing this system, however, requires a great amount of memory capacity to store the tone wave data, and inevitably become expensive.
As a solution to this shortcoming, there is a tone generating apparatus which has a wave memory to store in advance tone wave data corresponding a multiple-period waveform of a predetermined interval starting at the attack portion of a musical tone, reads the tone wave data from the beginning of the predetermined interval to the end thereof, and, after reading out the last piece of the tone wave data, repeatedly reads out tone wave data of a given interval at the end portion of the predetermined interval, thereby providing a sustaining musical tone. (The given interval will be hereinafter called "repetitive reading interval.")
According to this type of a tone generating apparatus, however, at the time wave data of the repetitive reading interval is repeatedly read out, it is difficult to accurately read out the wave data continuously in a given period, and discontinuity may occur at the repeated portion. The occurrence of such a discontinuous portion would make the continuity of a musical tone unnatural and would generate many unnecessary harmonic overtones even if the tone has a sinusoidal waveform, resulting in generation of low-quality musical tones.